Dual pressure control for a rotor brake actuator for vertical lift aircraft

ABSTRACT

In some aspects, a master cylinder assembly for vertical lift aircraft is configured to move pressurized fluid through a conduit in response to applied movement of an input lever. A low pressure relief valve can be connected to a first conduit to limit pressure to a low level. An isolation valve can be connected to the first conduit and configured to isolate the low pressure relief valve from the conduit when engaged. A high pressure relief valve can be connected to a second fluid conduit to limit pressure to a high level. In some aspects, a rotor brake actuator is fluidly connected to the first conduit and the second conduit and configured to engage a rotor brake in response to hydraulic fluid pressure.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/036,760 entitled “A Dual Pressure Control for a Rotor Brake Actuatorfor Vertical Lift Aircraft” filed on Sep. 25, 2013, the entire contentsof which is hereby incorporated by reference for all purposes.

TECHNICAL FIELD

The following description relates to control of a rotor brake actuatorsystem for vertical lift aircraft.

BACKGROUND

The rotor brake of a vertical lift aircraft such as a helicopter can beapplied with hydraulic actuators that use multiple hydraulic pressuresettings for different operational situations. In some cases, a firstpressure setting is a higher pressure than a second pressure setting.For example, a lower pressure (e.g. 220 psi) can be applied to the rotorbrake to slowly stop the rotor after landing. Likewise, a higherpressure (e.g. 800 psi) can be applied to the rotor brake to hold therotor from rotation during engine start-up.

SUMMARY

This description relates to a dual pressure brake actuator for verticallift aircraft. In some implementations, a rotor blade rotation controlmaster cylinder assembly for vertical lift aircraft includes a mastercylinder, a rotor brake actuator, a low pressure relief valve, a highpressure relief valve, and an isolation valve. The master cylinder isconfigured to be activated by movement of a rotor blade rotation controlhandle of a vertical lift aircraft to move pressurized hydraulic fluidthrough one or more conduits. The rotor brake actuator is connected tothe master cylinder and configured to engage a rotor brake of thevertical lift aircraft in response to receiving hydraulic fluid at ahydraulic fluid pressure from the master cylinder. The low pressurerelief valve fluidly is connected in parallel to the master cylinder andthe rotor brake actuator and configured to transmit pressurizedhydraulic fluid away from the rotor brake actuator in response to thehydraulic fluid pressure exceeding a first pressure threshold of the lowpressure relief valve. The high pressure relief valve is connected inparallel to the master cylinder, the rotor brake actuator and the lowpressure relief valve and configured to transmit pressurized hydraulicfluid away from the rotor brake actuator in response to the hydraulicfluid pressure exceeding a second pressure threshold of the highpressure relief valve. The second pressure threshold is higher than thefirst pressure threshold, and the low pressure relief valve can beisolated from the high pressure relief valve. The isolation valve isconnected in series to the master cylinder and the low pressure reliefvalve. The master cylinder is configured to push the hydraulic fluid ata first pressure to the rotor brake actuator in response to theisolation valve being open and to push the hydraulic fluid at a secondpressure that is lower than the first pressure in response to theisolation valve being closed.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an example hydraulic control circuit inan example rotor brake assembly.

FIG. 2 is a flowchart diagram of an example rotor braking process.

FIG. 3 is a flowchart diagram of an example rotor holding process. Likereference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

The rotor brake of a vertical lift aircraft such as a helicopter can beapplied with hydraulic actuators that use multiple hydraulic pressuresettings for different operational situations. For example, a firstpressure can be applied to the rotor brake to slowly stop the rotor,such as an engine shutdown after landing. Likewise, a second pressurecan be applied to the rotor brake to hold the rotor from rotation, e.g.,during engine start-up. In some implementations, the first pressure usedto slowly stop the rotor can be lower than the second pressure to holdthe rotor from rotation. In some typical implementations of a rotorbrake actuator, the first pressure setting can be provided by a manualcylinder, and the second pressure setting can be provided by anadditional separate motor-driven pump. The addition of a separatemotor-driven pump can add significant weight and cost to the rotor brakeassembly. In some typical implementations, the aircraft hydraulic systempressure is used to provide pressure to the rotor brake to slow, stop,or hold the rotor. Any additional components coupled to the aircrafthydraulic system can be sources of failure and stress on the system. Insome typical implementations, a pressure setting is achieved withmultiple strokes of a handle by a crewmember.

The example rotor blade rotation control assembly (the “rotor brakecontrol circuit assembly”) herein can provide multiple pressure settingsto a rotor brake without the use of aircraft hydraulic system pressureor an additional separate motor-driven pump. The example rotor brakecontrol circuit assembly also can provide adequate pressure from asingle stroke of the rotor blade rotation control handle (the “rotorbrake handle”). In some instances, the example rotor brake controlcircuit assembly described herein can provide multiple pressure settingsat a reduced weight and cost over other assemblies. Moreover, theexample rotor brake control circuit assembly can provide multiplepressure settings using only a single master cylinder. The example rotorbrake control circuit assembly can allow the pilot to precisely controlthe position of the rotor blade, e.g., to position the rotor blade andstop it at a specific position. In some implementations, the rotor brakecan be maintained for several hours with little to no loss in pressure.For example, the rotor brake can act as a parking brake for overnightstorage. This allows operators to not have to secure the blades manuallywhen parking for short periods of time.

FIG. 1 is a schematic of an example rotor brake actuator control circuitsystem 100. The example rotor brake actuator control circuit system 100includes a handle 102, a linkage 104, a master cylinder assembly 110,and plumbing conduit tube 130 f. The handle 102 is connected to thelinkage 104, which is connected to the master cylinder assembly 110 viainput lever 112. The input lever 112 is coupled to stops 114 a, 114 band a piston 116. The piston 116 resides inside a master cylinder 118and forms a main chamber 119 within the master cylinder 118. The mastercylinder assembly 110 also includes a reservoir 120 fluidly connected tothe master cylinder 118 through a check valve 122. The master cylinderassembly 110 includes an isolation valve 124, a low pressure reliefvalve 126, and a high pressure relief valve 128. The rotor brakeactuator control circuit system 100 also includes conduits 130 a, 130 b,130 c, 130 d, 130 e, 130 g and a rotor brake actuator 132. The mastercylinder 118, the reservoir 120, the check valve 122, the isolationvalve 124, the low pressure relief valve 126, the high pressure reliefvalve 128, and the rotor brake actuator 132 are all fluidly connectedvia conduits 130 a, 130 b, 130 c, 130 d, 130 e, 130 f, 130 g.

The low pressure relief valve 126, the high pressure relief valve 128,and the rotor brake actuator 132 are fluidly connected in parallel tomaster cylinder 118 and conduits 130 a and 130 b via conduits 130 c and130 d, 130 e, and 130 f, respectively. In some cases, the conduits 130a, 130 b, 130 c, 130 d, 130 e, 130 f, and 130 g are ports betweencomponents. In some cases, the conduits 130 a, 130 b, 130 c, 130 d, 130e, 130 f, and 130 g can include tubing or piping, or the conduits can becoupled through other components. The rotor brake actuator system 100can include additional or different features, and the components can beconfigured as shown in FIG. 1, or they may be configured in anothermanner. For example, the components of the master cylinder assembly 110can be incorporated into a single unit or separated into multiple units.

The handle 102 can be a lever that can be positioned between two extremepositions, “ON” and “OFF.” During operation, the handle 102 can bepositioned at either extreme position or at any position in between. Insome implementations, the handle 102 is a manually-operated lever thatcan be pivoted at one end. The handle 102 can be composed of two or morecomponents that together provide the mechanical action. The handle 102can be configured to operate with a load spread over the actuationdistance between ON and OFF.

The handle 102 is coupled to a linkage 104. The linkage 104 can be amechanical linkage that is configured to transfer the translation ofhandle 102 into the master cylinder assembly 110. The linkage 104 caninclude multiple links, bellcranks, cables, hydraulic systems or othercomponents. For example, the linkage 104 can include a cable couplingthe handle 102 to the input lever 112. In this case, translating thehandle 102 will translate the input lever 112 through the linkage 104.Input lever 112 is a mechanism coupled to linkage 104 and piston 116.The piston 116 resides within master cylinder 118. The input lever 112can include one or more levers, linkages, or components. Operation ofhandle 102 can actuate input lever 112 via linkage 104. As such, theactuation of input lever 112 can be proportional to the distance thehandle 102 is operated. Input lever 112 is coupled to piston 116 suchthat piston 116 is translated within cylinder 118 when input lever 112is actuated. The travel distance of input lever 112 is limited by stops114 a, 114 b. The stops 114 a, 114 b are rigid and fixed members thatprevent the input lever 112 from traveling beyond extreme positionscorresponding to ON and OFF. For example, the stops 114 a and 114 b arepositioned at positions that correspond to the ON and OFF positions ofthe handle 102. When the handle 102 is in the ON position, the inputlever 112 impinges against stop 114 a and when the handle 102 is in theOFF position, the input lever 112 impinges against the stop 114 b.

The main chamber 119 of the master cylinder 118 is fluidly connected toreservoir 120 via conduit 130 a. Reservoir 120 can contain a fluid suchas a hydraulic fluid. Check valve 122 is located in the conduit 130 abetween the main chamber 119 and the reservoir 120. Check valve 122allows fluid to flow from the reservoir 120 into the main chamber 119through conduit 130 a but prevents fluid from flowing in reverse fromthe main chamber 119 into the reservoir 120 through the same conduit 130a.

Fluid can be flowed from the reservoir 120 into the master cylinder 118during the stroke of the piston 116. For example, when the handle 102 isoperated from the ON position to the OFF position, the piston 116retracts and pulls fluid from the reservoir 120 into the main chamber119. When the handle 102 is operated from the OFF position into the ONposition, the piston 116 extends and ports fluid under pressure from themain chamber 119 into the conduit 130 a.

The conduit 130 a is fluidly connected to conduits 130 b, 130 c, 130 d,130 e, and 130 f. Low pressure relief valve 126 is connected to conduits130 c and 130 d, and high pressure relief valve 128 is connected toconduit 130 e. If the fluid pressure in the conduits 130 c and 130 dexceeds some first specified value with the isolation valve 124 open,the low pressure relief valve 126 will open and excess fluid will beported to reservoir 120 via conduit 130 g until the fluid pressure fallsbelow the specified value. If the fluid pressure in the conduit 130 eexceeds some second specified value with the isolation valve 124 closed,the high pressure relief valve 128 will open and excess fluid will beported to reservoir 120 via conduit 130 g until the fluid pressure fallsbelow the specified value. In this example, the first specified pressurevalue associated with the low pressure relief valve 126 is lower thanthe second specified pressure value associated with the high pressurerelief valve 128.

Rotor brake actuator 132 is connected to conduit 130 d. The rotor brakeactuator 132 can impart a braking force onto the rotor of a verticallift aircraft (not shown). The braking force could be provided by amechanism such as calipers that are actuated by the rotor brake actuator132. Thus, the fluid in conduits 130 a and 130 b is also ported underpressure into conduit 130 c during extension of the piston 116. Theisolation valve 124 is a two-position valve that operates to open andclose the conduit 130 d. The isolation valve 124 can include one or moresolenoids or other mechanical components. The isolation valve 124 can beengaged or disengaged after receiving a mechanical or electronic signal.The isolation valve 124 can be controlled by the aircraft's avionicssystem or a pilot-operated switch. For example, isolation valve 124 canbe engaged after receiving an electronic signal from the aircraft'savionics system. If the isolation valve 124 is open, the fluid can beported via conduit 130 c through isolation valve 124 and into lowpressure relief valve 126 via conduit 130 d. When the isolation valve124 is closed, then the low pressure relief valve 126 is no longerfluidly connected to conduit 130 b.

As the fluid flows into the rotor brake actuator 132 with continuedmovement of the handle 102 from the OFF position to the ON position, thepressure on the rotor brake actuator 132 increases. Returning the handle102 to the OFF position causes the fluid to withdraw from the rotorbrake actuator 132, resulting in a pressure drop in the rotor brakeactuator 132. The rotor brake actuator 132 imparts the braking forceproportionally to the pressure of the fluid in conduit 130 d.

When isolation valve 124 is closed, the pressure of the fluid in theconduits 130 a, 130 b, 130 c, 130 e, and 130 f is controlled (e.g.,limited) by the high pressure relief valve 128, and the maximum brakingforce imparted by the rotor brake actuator 132 is controlled by the highpressure relief valve 128. When isolation valve 124 is open, thepressure of the fluid in the conduits 130 a, 130 b, 130 c, 130 d, 130 e,and 130 f is controlled by both the low pressure relief valve 126 andthe high pressure relief valve 128. Since the low pressure relief valve126 has a lower pressure threshold value than the high pressure reliefvalve 128, then the maximum braking force imparted by the rotor brakeactuator 132 is controlled by the pressure threshold value of the lowpressure relief valve 126. Thus, if the isolation valve 124 is open, themaximum braking force imparted by the rotor brake actuator 132 is lowerthan the maximum force imparted when the isolation valve 124 is closed.

FIG. 2 is a flow chart diagram of example rotor braking process 200. Theexample rotor braking process 200 is a process to slow or stop therotors of a vertical lift aircraft. The example rotor braking process200 can be based on (e.g., implemented by) the example rotor brakeactuator control circuit system 100 described in FIG. 1. In someimplementations, the rotor braking process 200 corresponds to theconfiguration in FIG. 1 in which the isolation valve is open. In someinstances, an interlock prevents the rotor brake system from beingoperated when the engines are on. The interlock system can be controlledby the aircraft's avionics system, and include sensors or signalscoupled to aircraft components.

At 202, the isolation valve is de-energized. The isolation valve can bea valve such as isolation valve 124 in FIG. 1. The isolation valve canbe de-energized manually by the pilot. The isolation valve can also bede-energized automatically, such as in response to a signal from theaircraft's avionics system.

At 204, the engines of the vertical lift aircraft are turned off. Forexample, the engines can be turned off after the aircraft has landed.Without engine power, the rotors begin to slow.

At 206, the manual lever can be engaged. The manual lever can be ahandle or mechanism such as handle 102 shown in FIG. 1. The manual levercan be translated from an OFF position to an ON position or any positionin between. At the OFF position, no braking force is applied to therotor. At ON position, the maximum braking force is applied to therotor. An intermediate position between OFF and ON can provide anintermediate amount of braking force that can be proportional to thatintermediate position.

In some instances, the manual lever can be configured to produce maximumrotor braking after a single translation from OFF to ON. The manuallever can be configured to distribute manual pilot input work requiredthroughout the full travel of the handle to activate the master cylinderto minimize the maximum handle load at all handle positions. This cankeep pilot load to a minimal, manageable level. This can also allow adesign to be utilized that does not require pressure from the aircrafthydraulic system or require an electric motor driven pump.

At 208, the operation of the manual lever causes the rotor brakeactuator to engage, exerting a braking force on the rotor. For example,the rotor brake can include calipers coupled to the tail rotor driveshaft or other parts within the drive system. The rotor brake actuatorcan be controlled indirectly via the rotor brake control circuitassembly by the movement of the manual lever.

At 210, the braking force slows the rotor to a stop. In someimplementations, the handle can be moved towards ON or OFF to allow themaster cylinder to increase or decrease rotor brake pressure. This canallow the pilot to position the rotor blade and stop it at a specificposition. In some implementations, the rotor brake actuator pressure canbe maintained for several hours with little to no loss in pressure. Forexample, the rotor brake can act as a parking brake for overnightstorage.

FIG. 3 is a flow chart diagram of example rotor braking process 300. Theexample rotor braking process 300 is a process to hold the rotors of avertical lift aircraft upon initial engine start-up. The example rotorbraking process 300 can be based on the example rotor brake actuatorcontrol circuit system 100 described in FIG. 1.

The example rotor braking process 300 corresponds to a vertical liftaircraft which has its engines and systems initially turned off, and therotor brake disengaged. In some implementations, the rotor brake isstill engaged from a previous parking configuration. The pilot beginsthe engine startup procedure by turning on the power. At 302, theisolation valve is energized either manually via an electrical switch orautomatically via the avionics system. When the isolation valve isenergized, it closes and thus isolates the low-pressure relief valvefrom the rotor brake control circuit assembly.

At 304, the pilot sets the rotor brake. In the example rotor brakecontrol circuit assembly shown in FIG. 1, the handle 102 is set to thefully ON position. The low-pressure relief valve is isolated from therotor brake control circuit assembly by the isolation valve, so thepressure in the rotor brake control circuit assembly is limited by thehigh pressure relief valve. Thus, the rotor brake is applied at arelatively high pressure.

At 306, the pilot starts the first engine of the aircraft. The rotorsare held from turning by the rotor brake (at 308).

At 310, the pilot disengages the rotor brake by setting the handle tothe fully OFF position. Once the brake is disengaged, the rotors areable to turn under the power of the first engine. After the rotors arefree to turn, the pilot also can activate a second aircraft engine (at312).

At 314, the isolation valve is disengaged, either manually via anelectrical switch or automatically via the avionics system.

While this specification contains many details, these should not beconstrued as limitations on the scope of what may be claimed, but ratheras descriptions of features specific to particular examples. Certainfeatures that are described in this specification in the context ofseparate implementations can also be combined. Conversely, variousfeatures that are described in the context of a single implementationcan also be implemented in multiple embodiments separately or in anysuitable subcombination.

A number of examples have been described. Nevertheless, it will beunderstood that various modifications can be made. Accordingly, otherimplementations are within the scope of the following claims.

1-19. (canceled)
 20. A rotor blade rotation control master cylinderassembly for vertical lift aircraft, the assembly comprising: a mastercylinder configured to be activated by movement of a rotor bladerotation control handle of a vertical lift aircraft to move pressurizedhydraulic fluid through one or more conduits; a rotor brake actuatorconnected to the master cylinder and configured to engage a rotor brakeof the vertical lift aircraft in response to receiving hydraulic fluidat a hydraulic fluid pressure from the master cylinder; a pressurerelief valve fluidly connected in parallel to the master cylinder andthe rotor brake actuator, and configured to transmit pressurizedhydraulic fluid away from the rotor brake actuator in response to thehydraulic fluid pressure exceeding a pressure threshold of the pressurerelief valve; and an isolation valve connected in series to the mastercylinder and the pressure relief valve, the master cylinder configuredto push the hydraulic fluid at a first pressure to the rotor brakeactuator in response to the isolation valve being open and to push thehydraulic fluid at a second pressure that is higher than the firstpressure in response to the isolation valve being closed.
 21. The rotorblade rotation control master cylinder assembly of claim 20, wherein thepressure relief valve is a first pressure relief valve and the pressurethreshold is a first pressure threshold, and wherein the rotor bladerotation control master cylinder assembly further comprises a secondpressure relief valve connected in parallel to the master cylinder, therotor brake actuator and the first pressure relief valve, wherein thesecond pressure relief valve is configured to transmit pressurizedhydraulic fluid away from the rotor brake actuator in response to thehydraulic fluid pressure exceeding a second pressure threshold of thesecond pressure relief valve, the second pressure threshold higher thanthe first pressure threshold, and wherein the first pressure reliefvalve can be isolated from the second pressure relief valve.
 22. Therotor blade rotation control master cylinder assembly of claim 21,wherein the first pressure relief valve comprises a low pressure reliefvalve and the second pressure relief valve comprises a high pressurerelief valve.
 23. The rotor blade rotation control master cylinderassembly of claim 21, wherein the rotor brake actuator is configured tohold the rotor of the vertical lift aircraft at or below the secondpressure threshold.
 24. The rotor brake actuator of claim 4, wherein therotor brake actuator is configured to hold the rotor of the verticallift aircraft when the vertical lift aircraft is starting.
 25. The rotorblade rotation control master cylinder assembly of claim 20, furthercomprising one or more stops to prevent an input lever from translatingbeyond a certain distance.
 26. The rotor blade rotation control mastercylinder assembly of claim 20, wherein the hydraulic fluid in the rotorblade rotation control master cylinder assembly can provide apressurized volume of fluid to engage the rotor brake in response to asingle translation of the rotor blade rotation control handle.
 27. Therotor blade rotation control master cylinder assembly of claim 20,wherein the isolation valve includes a solenoid.
 28. The rotor bladerotation control master cylinder assembly of claim 20, wherein the rotorbrake actuator is configured to slow the rotor of the vertical liftaircraft at or below the pressure threshold.
 29. The rotor brakeactuator of claim 28, wherein the rotor brake actuator is configured toslow the rotor of the vertical lift aircraft when the vertical liftaircraft is stopped.
 30. The rotor blade rotation control mastercylinder assembly of claim 20, wherein the rotor blade rotation controlmaster cylinder assembly is configured to maintain sufficient pressureto prevent rotor motion for a period of time after stopping.
 31. A rotorblade rotation control master cylinder assembly for vertical liftaircraft, the assembly comprising: a master cylinder configured to beactivated by a pressure of a rotor blade rotation control handle of avertical lift aircraft to move pressurized hydraulic fluid through oneor more conduits, and configured to move pressurized fluid into a rotorbrake actuator; a pressure relief valve fluidly connected to the mastercylinder and configured to transmit hydraulic fluid in response to thehydraulic fluid pressure exceeding a pressure threshold of the pressurerelief valve; and an isolation valve connected in series to the mastercylinder and the pressure relief valve configured to allow the mastercylinder to move pressurized hydraulic fluid at a first pressure inresponse to the isolation valve being open and to move the pressurizedhydraulic fluid at a second pressure that is higher than the firstpressure in response to the isolation valve being closed.
 32. The rotorblade rotation control master cylinder assembly of claim 31, wherein thepressure relief valve is a first pressure relief valve and the pressurethreshold is a first pressure threshold and further comprising a secondpressure relief valve connected in parallel to the master cylinder andthe first pressure relief valve, wherein the second pressure reliefvalve is configured to transmit hydraulic fluid in response to thehydraulic fluid pressure exceeding a second pressure threshold of thesecond pressure relief valve, the second pressure threshold higher thanthe first pressure threshold.
 33. The rotor blade rotation controlmaster cylinder assembly of claim 31, wherein the hydraulic fluid in therotor blade rotation control master cylinder assembly can be pressurizedto engage a rotor brake in response to a single translation of the rotorblade rotation control handle.
 34. The rotor blade rotation controlmaster cylinder assembly of claim 31, wherein the volume of pressurizedhydraulic fluid actuates the rotor brake actuator.
 35. The rotor bladerotation control master cylinder assembly of claim 34, wherein the rotorbrake actuator is configured to slow the rotor of the vertical liftaircraft at or below the pressure threshold.
 36. The rotor brakeactuator of claim 35, wherein the rotor brake actuator is configured toslow the rotor of the vertical lift aircraft when the vertical liftaircraft is stopped.
 37. The rotor blade rotation control mastercylinder assembly of claim 32, wherein the rotor brake actuator isconfigured to hold the rotor of the vertical lift aircraft at or belowthe second pressure threshold.
 38. The rotor brake actuator of claim 37,wherein the rotor brake actuator is configured to hold the rotor of thevertical lift aircraft when the vertical lift aircraft is starting. 39.The rotor blade rotation control master cylinder assembly of claim 31,wherein the rotor blade rotation control master cylinder assembly isconfigured to maintain sufficient pressure to prevent rotor motion for aperiod of time after stopping.